Conventional drug discovery and development takes an average of 12 years and costs hundreds of millions of dollars for each new drug that reaches patients. Repositioning of approved drugs and clinical-stage compounds with existing preclinical and clinical data can greatly expedite the process, particularly for rare, low-prevalence diseases and the more wide-spread diseases endemic to the developing world that are otherwise typically neglected by the pharmaceutical industry. We have employed new technologies and approaches for screening, such as phenotypic cell-based disease models using patient-derived induced pluripotent stem (iPS) cells and high-content screening platforms. Our approach is to collaborate with leading investigators from across the research ecosystem, including at NIH, academic institutions, and biopharmaceutical companies. Our objectives include (1) identification of drug targets or disease phenotypes for assay development; (2) assay development and optimization for high-throughput screening; (3) drug repurposing screening to identify active compounds that reduce disease phenotypes; (4) confirmation of compound activity using in vitro assays and animal models; and (5) advancement of any newly-identified candidate compounds to clinical trials for the treatment of rare and neglected diseases. We have performed drug repurposing screens for multiple projects across a range of therapeutic areas, including rare genetic disorders, bacterial and viral infectious diseases, and rare molecularly-targeted cancers. INFECTIONS WITH DRUG RESISTANT BACTERIA: Infections with multidrug-resistant (MDR) organisms have emerged as a significant worldwide public health crisis. The incidence is increasing partially due to the selective pressure from widespread use of antibiotics in both humans and animals. The Centers for Disease Control and Prevention (CDC) reports that many of the most urgent and serious antibiotic-resistant bacteria threaten patients while they are being treated in healthcare facilities for other conditions, and may lead to sepsis or death. The common antibiotic-resistant bacteria seen in hospitals are carbapenem-resistant Enterobacteriaceae (CRE), methicillin-resistant Staphylococcus aureus (MRSA), ESBL-producing Enterobacteriaceae (extended-spectrum -lactamases), vancomycin-resistant Enterococcus (VRE), multidrug-resistant Pseudomonas aeruginosa and multidrug-resistant Acinetobacter. Several outbreaks of severe infectious diseases occurred in the last six years including those caused by carbapenem-resistant Klebsiella pneumoniae, Exserohilum rostratum in contaminated methylprednisolone solutions, Ebola virus, Zika virus, and emerging artemisinin-resistant malaria. Searching for effective therapeutics is an unmet medical need. We have performed high throughput screening for drug repurposing and synergistic drug combinations for these emerging pathogens that resulted in identification of new therapeutics with potential for immediate clinical application. We have screened the approved drug collection and thousands of synergistic drug combinations against drug resistant K. pneumoniae. We also performed screens against ten clinically relevant Gram-negative strains including K. pneumoniae (KPNIH776 and KPNIH892), Acinetobacter baumannii (ABNIH144, ABNIH233 and ABNIH333), P. aeruginosa (PANIH338 and PANIH668), Citrobacter freundii (CFB10), Enterobacter cloacae (ECB2), and Escherichia coli (ECOB11). The activities of most approved drugs identified from the screens were too weak for use as clinical treatment. We then applied the synergistic drug combination approach and found that three-drug combination is more effective in suppressing the growth of these multidrug resistant bacteria. Three sets of 3-drug combinations were identified as active against all ten strains: colistin-auranofin-ceftazidime, colistin-auranofin-rifabutin, and rifabutin-colistin-imipenem. Results have been published with potential clinical applications. EBOLA INFECTION: Ebola infection results in serious illness, and is fatal in more than half of all cases, due to a lack of an effective anti-infection therapy. Recently, new Ebola infections were reported by WHO in May 2017 in Democratic Republic of the Congo. Although several drug repurposing screens have been performed and a number of drugs reported, these identified drugs are not potent enough for clinical application to treat Ebola infection. We have employed an alternative strategy to look for synergistic drug combinations. We screened thousands of 2- and 3-drug combinations using approved drug collections. Two-drug combinations were not potent or effective enough for clinical application. However, two potential 3-drug combinations were identified: toremifene-clarithromycin-posaconazole (TCP) and toremifene-mefloquine-posaconazole (TMP). PERSISTENT BORRELIA BURGDORFERI: Persistent Borrelia burgdorferi is involved in the drug resistance of Lyme disease. We have identified 60 primary hits that killed the persistent bacteria. We also found synergy between doxycycline (standard care) and eleven additional compounds. We are continuing to study of mechanisms of action for these compounds and combinations. DRUG RESISTANT CANCER: Drug resistant cancer causes severe clinical problems that often results in death. We performed drug repurposing screens for multiple resistant cell lines of ovarian cancer, cervical cancer, uterine cancer, liver cancer, pancreatic cancer, colon cancer, and lung cancer. We have identified a number of approved drugs and bioactive compounds that re-sensitized resistant cancer cells to the standard care oncology drug regimens. Using these identified compounds, we have found the mechanisms of drug resistance in several cancer cell lines related to autophagy, apoptosis, and immune-response pathways. The study helped identify several potential new drug targets to treat resistant cancers.